On Mon, May 22, 2017 at 10:35 AM, Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > Kmemleak requires that vmalloc'ed objects have a minimum reference count > of 2: one in the corresponding vm_struct object and the other owned by > the vmalloc() caller. There are cases, however, where the original > vmalloc() returned pointer is lost and, instead, a pointer to vm_struct > is stored (see free_thread_stack()). Kmemleak currently reports such > objects as leaks. > > This patch adds support for treating any surplus references to an object > as additional references to a specified object. It introduces the > kmemleak_vmalloc() API function which takes a vm_struct pointer and sets > its surplus reference passing to the actual vmalloc() returned pointer. > The __vmalloc_node_range() calling site has been modified accordingly. > > An unrelated minor change is included in this patch to change the type > of kmemleak_object.flags to unsigned int (previously unsigned long). > > Reported-by: "Luis R. Rodriguez" <mcgrof@xxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxxxx> > Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> > --- > > Hi, > > As per [1], I added support to use pointers to vm_struct as an > alternative way to avoid false positives when the original vmalloc() > pointer has been lost. This is slightly harder to reason about but it > seems to work for this use-case. I'm not aware of other cases (than > free_thread_stack()) where the original vmalloc() pointer is removed in > favour of a vm_struct one. > > An alternative implementation (simpler to understand), if preferred, is > to annotate alloc_thread_stack_node() and free_thread_stack() with > kmemleak_unignore()/kmemleak_ignore() calls and proper comments. > I personally prefer the option in this patch. It keeps the special case in kmemleak and the allocation code rather than putting it in the consumer code. Also, I want to add an API at some point that vmallocs some memory and returns the vm_struct directly. That won't work with explicit annotations in the caller because kmemleak might think it's leaked before the caller can execute the annotations. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
